U.S. patent application number 11/583740 was filed with the patent office on 2008-01-10 for high-frequency probe card and transmission line for high-frequency probe card.
This patent application is currently assigned to MJC Probe Incorporation. Invention is credited to Te-Chen Feng, Chih-Hao Ho, Wei-Cheng Ku, Hsin-Hung Lin.
Application Number | 20080007278 11/583740 |
Document ID | / |
Family ID | 38918577 |
Filed Date | 2008-01-10 |
United States Patent
Application |
20080007278 |
Kind Code |
A1 |
Ku; Wei-Cheng ; et
al. |
January 10, 2008 |
High-frequency probe card and transmission line for high-frequency
probe card
Abstract
A high-frequency probe card includes a circuit board having
signal circuits and grounding circuits, transmission lines each
having a bi-wire structure including a first lead wire for
transmitting high-frequency signal and a second lead wire connected
to the grounding circuits, and signal probes. High-frequency test
signal provided by a test machine to the signal circuits can be
transmitted to the signal probes through the first lead wires.
Since the grounding circuits and second lead wires are provided
adjacent to the signal circuits and first lead wires respectively,
the high-frequency signal can be efficiently transmitted and the
characteristic impedance matching can be maintained during
high-frequency signal transmission. The bi-wire structure of the
transmission lines has a diameter equal to or less than 1
millimeter, thereby allowing installation of a big number of the
transmission lines such that the high-frequency test for a big
number of electronic elements can be realized.
Inventors: |
Ku; Wei-Cheng; (Hsinchu
Hsiang, TW) ; Lin; Hsin-Hung; (Hsinchu Hsiang,
TW) ; Ho; Chih-Hao; (Hsinchu Hsiang, TW) ;
Feng; Te-Chen; (Hsinchu Hsiang, TW) |
Correspondence
Address: |
BROWDY AND NEIMARK, P.L.L.C.;624 NINTH STREET, NW
SUITE 300
WASHINGTON
DC
20001-5303
US
|
Assignee: |
MJC Probe Incorporation
Chu-Pei City
TW
|
Family ID: |
38918577 |
Appl. No.: |
11/583740 |
Filed: |
October 20, 2006 |
Current U.S.
Class: |
324/756.03 |
Current CPC
Class: |
G01R 1/06772 20130101;
G01R 31/2889 20130101 |
Class at
Publication: |
324/754 |
International
Class: |
G01R 31/02 20060101
G01R031/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 6, 2006 |
TW |
9514686 |
Claims
1. A high-frequency probe card comprising: a circuit board having a
plurality of signal circuits and a plurality of grounding circuits
respectively spaced from said signal circuits at a predetermined
pitch and respectively electrically connected to a zero potential;
a plurality of transmission lines disposed on said circuit board,
each of said transmission lines having a first lead wire and a
second lead wire, which are made of metal, spaced from each other
at a predetermined pitch and respectively electrically connected to
one of said signal circuits and one of said grounding circuits; and
a plurality of signal probes and at least one grounding probe
respectively made of metal, said signal probes being respectively
electrically connected to the first lead wires of said transmission
lines, said at least one grounding probe being electrically
connected to the zero potential.
2. The high-frequency probe card as claimed in claim 1, which said
circuit board has a top surface, a bottom surface opposite to said
top surface, an outer test zone and an inner jumping zone, wherein
the said grounding circuits on the top surface within the test zone
are respectively spaced around said signal circuits at a
predetermined pitch.
3. The high-frequency probe card as claimed in claim 2, wherein
said circuit board has a plurality of solder pads arranged on said
top surface and said bottom surface within said jumping zone, said
solder pads including a plurality of signal solder pads and a
plurality of grounding solder pads, the signal solder pads and the
grounding solder pads at said top surface being respectively
connected to the signal solder pads and the grounding solder pads
at said bottom surface by said signal circuits and said grounding
circuits respectively, the signal solder pads at said top surface
being respectively connected to the first lead wires of said
transmission lines, the signal solder pads at said bottom surface
being respectively connected to said signal probes.
4. The high-frequency probe card as claimed in claim 1, further
comprising a probe holder disposed at said circuit board for
holding said signal probes and said at least one grounding probe,
said probe holder having a grounding plane made of an electrically
conductive material, wherein said at least one grounding probe is
electrically connected to the grounding plane of said probe
holder.
5. The high-frequency probe card as claimed in claim 4, further
comprising a plurality of grounding wires, each of which is
parallel arranged with one of said signal probes and electrically
connected to said at least one grounding circuit of said circuit
board and said grounding plane of said probe holder.
6. The high-frequency probe card as claimed in claim 5, wherein
each of said signal probes is axially covered with an electrically
insulating covering, which has a thickness equal to the pitch
between the signal probe and the grounding wire.
7. The high-frequency probe card claimed in claim 4, wherein said
probe holder comprises a locating ring made of an electrically
insulating and shock absorbing material for holding bodies of said
grounding probes and bodies of said signal probes, keeping tips of
said grounding probes and tips of said signal probes be suspended
in an annular opening of the locating ring.
8. The high-frequency probe card as claimed in claim 7, wherein
said locating ring is mounted to said circuit board; said grounding
plane is provided at a peripheral wall of said locating ring.
9. The high-frequency probe card as claimed in claim 1, wherein
said circuit board has a ring shape with a center hole in which a
probe holder is accommodated, wherein said probe holder has a
bottom wall made of an insulating material, a top open chamber, an
insulating layer covered on a top surface of said bottom wall;
wherein said transmission lines extend from said circuit board to
said top open chamber of said probe holder, having the first lead
wires of said transmission lines respectively be inserted through
said insulating layer and said bottom wall and exposed on a bottom
surface of said bottom wall of said probe holder.
10. The high-frequency probe card as claimed in claim 9, wherein
said signal probes are mounted to said bottom surface of said probe
holder and respectively connected to the first lead wires of said
transmission lines.
11. The high-frequency probe card as claimed in claim 10, wherein
said circuit board comprises at least one grounding wire made of
metal and electrically connected to said grounding circuits; the
grounding wire extends from said circuit board to said top open
chamber of said probe holder and is inserted through said
insulating layer and said bottom wall of said probe holder and
exposed on said bottom surface of said probe holder.
12. The high-frequency probe card as claimed in claim 11, wherein
said probe holder further comprises a grounding plane covered on
said insulating layer and made of metal; the second lead wires of
said transmission lines and said grounding wire are electrically
connected to said grounding plane.
13. The high-frequency probe card as claimed in claim 12, wherein
said at least one grounding probe is mounted to said bottom surface
of said probe holder and connected to said at least one grounding
wire of said circuit board.
14. The high-frequency probe card as claimed in claim 10, wherein
said probe holder has an upright sidewall made of metal and abutted
against a periphery wall of the center hole of said circuit board;
the second lead wires of said transmission lines and said at least
one grounding probe are electrically connected to the upright
sidewall of said probe holder.
15. A transmission line for a high-frequency probe card,
comprising: a first lead wire of metal for transmitting a
high-frequency signal and maintaining a predetermined
characteristic impedance of said high-frequency signal; a second
lead wire of metal spaced from said first lead wire at a
predetermined pitch for connecting to a zero potential; and a first
electrically insulating covering axially covered on said first lead
wire.
16. The transmission line as claimed in claim 15, wherein said
first electrically insulating covering has an inner diameter
substantially equal to a diameter of said first lead wire.
17. The transmission line as claimed in claim 16, wherein the
predetermined pitch between the first lead wire and the second lead
wire is equal to a wall thickness of the first electrically
insulating covering.
18. The transmission line as claimed in claim 15, wherein the
predetermined pitch between said first lead wire and said second
lead wire is smaller than 1 mm.
19. The transmission line as claimed in claim 15, further
comprising a second electrically insulating covering axially
covered on said second lead wire and abutted with the first
electrically insulating covering.
20. The transmission line as claimed in claim 15, further
comprising an electrically insulating sleeve axially sleeved onto
said first lead wire that is axially covered by the first
electrically insulating covering and said second lead wire.
21. The transmission line as claimed in claim 20, wherein said
electrically insulating sleeve has an inner diameter substantially
equal to a sum of an outer diameter of said first electrically
insulating covering and a diameter of said second lead wire.
22. The transmission line as claimed in claim 19, further
comprising an electrically insulating sleeve axially sleeved onto
said first and second electrically insulating coverings; wherein
said electrically insulating sleeve has an inner diameter
substantially equal to a sum of outer diameters of said first and
second electrically insulating coverings.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to probe cards and more
particularly, to a high-frequency probe card that requires less
installation space for transmission lines.
[0003] 2. Description of the Related Art
[0004] A probe card is a testing card having a circuit board and a
plurality of downwardly extending probes for probing the contact
pads on an integrated semiconductor wafer for transmitting test
signals subject to the control of a software from a test machine to
the integrated circuit of the wafer, thereby performing the wafer
level test automatically. The density of the arrangement of the
probes must be corresponding to the pitch of the contact pads on
the wafer. Further, in order to fit various wafers manufactured by
various integrated circuit technologies, the design of the circuit
board of a probe card may not use a specific wiring layout for
signal transmission between the test machine and the probes.
Alternatively, a jumping connection structure of transmission lines
may be used and connected between the lead wires probed by the test
machine and the probes for allowing signal transmission from the
test machines to the probes.
[0005] Comparing to the probes of a probe card, the diameter of the
transmission line is much greater than the diameter of the probe.
When connecting the transmission lines to the probes respectively,
the transmission lines become densely arranged in the area adjacent
to the probes. Following the sophisticated and versatile circuit
design of semiconductor wafer, probe cards must be made having a
high count of probes to meet wafer level test requirements of
multiple test-items for testing circuit device characteristics
quickly. In consequence, the installation density of the jumping
connection structure of transmission lines becomes critical. In
some cases, for example, in the cantilever-type probe card shown in
FIG. 12, transmission lines are stacked and crossed over one
another for positive connection to their respective probes. This
design complicates the module engineering of jumping transmission
lines and increases its difficulty level. As considering a coaxial
cable for the transmission of high-frequency signals, an
electrically insulating plastic layer having a predetermined wall
thickness surrounds an axial wire and also be surrounded by an
electrically grounded metal shield so that the characteristic
impedance of the transmitted signal propagating by the axial wire
can be maintained. However, in order to prevent the transmitted
signal from characteristic impedance mismatching that may be
resulted from dielectric loss of a parasitic capacitance induced by
the plastic layer, the plastic layer must have a certain wall
thickness determined subject to its dielectric constant. No matter
what kinds of the plastic layer of a coaxial cable used, the entire
diameter of the coaxial cable is much greater than its axial wire,
thus requiring more installation space of the transmission lines.
Therefore, a conventional high-frequency probe card does not allow
the dense arrangement of the probes respectively connecting to the
coaxial cables for high-frequency test probing.
[0006] A probe card may install multi-layer circuit structure of
the so-called space converter. For example, FIG. 13 shows a
conventional vertical-type probe card 5. According to this design,
the vertical-type probe card 5 comprises a circuit board 5a, a
space converter 5b, and a plurality of probes 5c stacked at
different elevations. The circuit board 5a has arranged thereon a
predetermined circuit layout extending from the top surface to the
bottom surface for signal transmission. The circuit at the top
surface of the circuit board 5a is adapted for the contact of the
probing pins 6 of the test machine. The circuit at the bottom
surface of the circuit board 5a is for the connection of the space
converter 5b. The space converter 5b is formed of a MLC
(Multi-Layer Ceramic) or MLO (Multi-Layer Organic) structure. A
plurality of electric contacts are arranged on the top and bottom
sides of the space converter 5b with different pitches for the
respectively electrical connection to the circuit board 5a and the
probes 5c. The space converter 5b has laminated circuit layout
therein formed by means of the application of semiconductor
manufacturing. The pitch of the circuit layout of the space
converter 5b that is closer to the probes 5c is relatively smaller
so that the lead wires of the circuit board 5a can be respectively
conducted to the densely arranged probes 5c, achieving the space
conversion effect between the circuit board 5a and the probes 5c to
probe the densely arranged electronic devices on the wafer 7.
However, the fabrication of the space converter is subject to the
application of a micro electromechanical process or thin-film
manufacturing, and a specific insulating material like a ceramic
substrate may be needed for the base, thereby resulting in a high
manufacturing cost greater than the fabrication of the circuit
board. There is a demand for a high-frequency probe card that uses
an economic circuit structure for signal transmission, maintains
characteristic impedance of high-frequency signaling and provides
high reliability testing.
SUMMARY OF THE INVENTION
[0007] The present invention has been accomplished under the
circumstances in view. It is therefore an objective of the present
invention to provide a high-frequency probe card, which transmits
high-frequency test signals to probes by using a high quality
transmission line structure that has a low installation density,
thereby effectively simplifying module engineering of setting
transmission lines and improving test quality of the high-frequency
probe card.
[0008] To achieve this objective of the present invention, the
high-frequency probe card comprises a circuit board, a plurality of
transmission lines, a plurality of signal probes and at least one
grounding probe. The circuit board comprises a plurality of signal
circuits and grounding circuits respectively spaced from the signal
circuits at a predetermined pitch. The grounding circuits are
electrically connected to a zero potential of a test machine to
block any outside interference away from the respectively
surrounded signal circuits and provide the test signals carried by
the respective signal circuits with the reference potential of
their respective characteristic impedance. The transmission lines
are disposed on the circuit board, each having a first lead wire
and a second lead wire respectively made of electrically conducting
materials and spaced from each other at a predetermined pitch and
electrically connected to the signal circuit and the grounding
circuit of the circuit board respectively. The signal probes and
the at least one grounding probe are made of hard metal materials
and electrically connected to the first lead wire and the zero
potential of the test machine respectively. The signal probes and
the at least one grounding probe each have one end for connection
to the circuit board and the other end for contacting a respective
conducting bump pad at the test sample.
[0009] Further scope of applicability of the present invention will
become apparent from the detailed description given hereinafter.
However, it should be understood that the detailed description and
specific examples, while indicating preferred embodiments of the
invention, are given by way of illustration only, since various
changes and modifications within the spirit and scope of the
invention will become apparent to those skilled in the art from
this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The present invention will become more fully understood from
the detailed description given herein below and the accompanying
drawings which are given by way of illustration only, and thus are
not limitative of the present invention, and wherein:
[0011] FIG. 1 is a top view of a high-frequency probe card
according to a first preferred embodiment of the present
invention;
[0012] FIG. 2 is a bottom view of the high-frequency probe card
according to the first preferred embodiment of the present
invention;
[0013] FIG. 3 is a schematic drawing showing the structure of the
high-frequency probe card according to the first preferred
embodiment of the present invention;
[0014] FIG. 4 is a schematic cross sectional view of a transmission
line for the high-frequency probe card according to the first
preferred embodiment of the present invention;
[0015] FIG. 5 is a frequency characteristic curve obtained from the
transmission lines of the high-frequency probe card according to
the first preferred embodiment of the present invention;
[0016] FIG. 6 is a schematic cross sectional view of a transmission
line for a high-frequency probe card according to a second
preferred embodiment of the present invention;
[0017] FIG. 7 is a schematic cross sectional view of a transmission
line for a high-frequency probe card according to a third preferred
embodiment of the present invention;
[0018] FIG. 8 is a schematic perspective view of a transmission
line for a high-frequency probe card according to a fourth
preferred embodiment of the present invention;
[0019] FIG. 9 is a schematic drawing showing the structure of a
high-frequency probe card according to a fifth preferred embodiment
of the present invention;
[0020] FIG. 10 is a schematic drawing showing the structure of a
high-frequency probe card according to a sixth preferred embodiment
of the present invention;
[0021] FIG 11 is a schematic drawing showing the structure of a
high-frequency probe card according to a seventh preferred
embodiment of the present invention;
[0022] FIG. 12 is a top view of a cantilever type probe card
according to the prior art, and
[0023] FIG. 13 is a schematic drawing showing the structure of a
vertical type probe card according to the prior art.
DETAILED DESCRIPTION OF THE INVENTION
[0024] As shown in FIGS. 1-3, a high-frequency probe card 1 in
accordance with a first preferred embodiment of the present
invention comprises a circuit board 10, a probe holder 20, a
plurality of transmission lines 30, a plurality of high-frequency
probes 40, and a plurality of grounding probes 50. The circuit
board 10 has a top surface 101 and a bottom surface 102, defining
an annular outer test zone 103 and an annular inner jumping zone
104 concentrically disposed within the test zone 103. The circuit
board 10 has arranged thereon electronic circuits. A plurality of
solder pads 105 and 106 are respectively arranged on the top
surface 101 and bottom surface 102 within the jumping zone 104. The
electronic circuits of the circuit board 10 at the top surface 101
within the test zone 103 are electrically connected to a test
machine (not shown), which is controlled to output a high-frequency
test signal to the high-frequency probe card 1. The solder pads 105
at the top surface 101 are respectively electrically connected to
the transmission lines 30 and to the solder pads 106 at the bottom
surface 102. The solder pads 106 at the bottom surface 102 are
respectively electrically connected to the probes 40 and 50.
[0025] Referring to FIG. 1 again, the electronic circuits of the
circuit board 10 include a plurality of signal circuits 11 and
grounding circuits 12. The grounding circuits 12 on the top surface
101 within the test zone 103 are respectively spaced around the
signal circuits 11 at a predetermined pitch. These signal circuits
11 are adapted to transmit the test signal from the aforesaid test
machine. The grounding circuits 12 are electrically connected to
the zero potential of the test machine, for blocking any outside
interference away from the respectively surrounded signal circuits
12 and providing the test signals carried by the respective signal
circuits 12 with the reference potential of their respective
characteristic impedance. Please refer also to FIG. 3. Inside the
circuit board 10, the grounding circuits 12 within the test zone
103 have a co-planar arrangement of lead wires respectively spaced
below the signal circuits 11 at a predetermined distance. Each of
the signal circuits 11 and grounding circuits 12 within the jumping
zones 104 of the circuit board 10 directly contacts with a solder
pad 105 at the top surface 101 and a solder pad 106 at the bottom
surface 102.
[0026] Referring to FIGS. 2 and 3 again, the probe holder 20 is
installed in the bottom surface 102 of the circuit board 10 and
surrounded by the jumping zone 104, having a grounding plane 21 and
a locating ring 22. The grounding plane 21 is a flat annular
surface made of an electrically conducting material and formed on
the bottom surface 102 of the circuit board 10. The locating ring
22 is provided on the grounding plane 21 to hold the body of each
of the probes 40 and 50, keeping the tip of each of the probes 40
and 50 be suspended in an annular opening 220 surrounded by the
locating ring 22. The locating ring 22 is made of an electrically
insulating and shock absorbing material, for example, epoxy
resin.
[0027] Referring to FIG. 3 again, the transmission lines 30 are
respectively connected to the electronic circuits in the inner side
of the test zone 103 of the circuit board 10, and extended to the
jumping zone 104 to respectively connect to the solder pads 105 at
the top surface 101. Each transmission line 30 has a first lead
wire 31 and a second lead wire 32. Each of the first lead wire 31
and the second lead wire 32 is a metal wire axially wrapped with an
electrically insulating covering 311 or 321, namely the first
covering 311 or the second covering 321. Each transmission line 30
further comprises a sleeve 33 surrounding the first lead wire 31
that is wrapped by the first covering 311 and the second lead wire
32 that is wrapped by the second covering 312 and holding them in
place. Each of the first lead wire 31 and the second lead wire 32
has a first end 312 or 322 and a second end 313 or 323. The first
end 312 and second end 313 of the first lead wire 31 are
respectively connected to the signal circuit 11 and a signal solder
pad 105a of the solder pads 105 at the top surface 101. The first
end 322 and second end 323 of the second lead wire 32 are
respectively connected to the grounding circuit 12 and a grounding
solder pad 105b of the solder pads 105 at the top surface 101.
Please refer also to FIG. 4. The coverings 311 and 321 of each
transmission line 30 protect their respective lead wires 31 and 32
against oxidation and contamination, and provide a specific pitch
to keep the lead wires 31 and 32 in parallel within the sleeve 33.
The pitch between the lead wires 31 and 32 is equal to the combined
wall thickness of the coverings 311 and 321.
[0028] Referring to FIGS. 2 and 3 again, each of the high-frequency
probes 40 comprises a signal probe 41, a grounding wire 42, and a
sleeve 43. The signal probe 41 is made of a hard metal material,
having one end electrically connected to a signal solder pad 106a
of the solder pads 106 at the bottom surface 102 and the other end
terminated in a tip 410 for touching a signal bump pad at the test
sample (not shown). The signal probe 41 is also axially covered
with a covering 411 that functions in the same manner as the
coverings 311 of the transmission lines 30. The front section of
the signal probe 41 is arranged between the locating ring 22 and
the solder pads 106, and parallel with the grounding wire 42, and
surrounded with the grounding wire 42 by the sleeve 43. The two
distal ends of the grounding wire 42 are respectively connected to
a grounding solder pad 106b of the solder pads 106 and the
grounding plane 21. Because the signal solder pads 106a and the
grounding solder pads 106b are directly electrical connected to the
respective signal solder pads 105a and the grounding solder pads
105b through the circuit board 10, the signal probe 41 of the
high-frequency probe 40 can transmit the test signal passed by the
transmission line 30 to the test sample. The grounding wire 42 of
each high-frequency probe 40 is grounded, maintaining the
characteristic impedance of the signal passed by the associated
signal probe 41. The grounding probe 50 is made of a hard metal
material, having one end electrically connected to one grounding
solder pad 106b and the other end terminated in a tip 500 for
touching a grounding bump pad at the test sample (not shown).
Further, the body of each grounding probe 50 is electrically
connected to the grounding plane 21 of the probe holder 20.
Therefore, all grounding potentials of the high-frequency probe
card 1 common on the grounding plane 21.
[0029] After connection of the electronic circuits at the test zone
103 of the high-frequency probe card 1 to the test machine, the
signal circuit 11 transmits the test signal to the first lead wire
31 then to the signal probe 41. Because the grounding circuits 12,
the second lead wires 32 and the grounding wires 42 are arranged
nearby the signal lines 11, the first lead wires 31 and the signal
probes 41 respectively, the invention allows effective transmission
of high-frequency test signals, maintains the characteristic
impedance matching and eliminates unnecessary electric coupling
effect. Therefore, the high-frequency probe card 1 provides a high
reliability test with high-frequency signal transmission. Further,
because each transmission line 30 has a parallel bi-wire structure,
characteristic impedance of the transmitted signal is determined
subject to the pitch of the wires. The distance between the first
lead wire 31 and the second lead wire 32 according to the present
invention is equal to the combined wall thickness of the insulating
coverings 311 and 321, which can be kept smaller than 1 mm while
controlling the characteristic impedance of the test signal within
the first lead wire 31 to the standard level as an coaxial cable,
i.e., 50-75 Ohm. Therefore, the invention effectively maintains the
characteristic impedance of the test signal within the first lead
wire 31 without the use of an insulating material with several
millimeter of the wall thickness as the insulation tube used in a
conventional coaxial cable. Please refer to the frequency
characteristic curve of the transmission lines 30 in FIG. 5. As
illustrated, the return loss curve S11 of the transmission line 30
measured from 100 MHz to high-frequency range of a few GHz shows an
insignificant return loss, i.e., it shows a satisfactory impedance
match at the high-frequency range. Further, the insertion loss
curve S21 of the transmission line 30 in FIG. 5 shows the passband
threshold frequency at gain -3 dB can be as high as 1.2 GHz, having
an excellent high-frequency signal transmission quality. Therefore,
the high-frequency probe card 1 has low loss and excellent
impedance match during transmission of a high-frequency signal.
Further, because the diameter of the transmission line 30 is
smaller than 1 mm, the count of the transmission lines 30 in the
jumping zone 104 can be relatively high for passing high-frequency
test signals to a big number of test samples at a time without
causing an installation problem of setting the jumped transmission
lines that also may affect a probe card's circuit quality.
[0030] Because the transmission lines of the present invention are
designed to use a bi-wire structure to improve high frequency
transmission quality and to lower installation density, they can be
made in other alternate forms. FIGS. 6-8 show transmission lines
34, 36, 38 according to second, third and fourth embodiments of the
present invention.
[0031] As shown in FIG. 6, the transmission line 34 comprises the
lead wires 31 and 32, the insulating covering 311 surrounding the
first lead wire 31 and an insulating sleeve 35 surrounding outside
and holding the first lead wire 31 and the second lead wire 32
firmly in parallel. The pitch between the first lead wire 31 and
the second lead wire 32 is equal to the wall thickness of the
covering 311, and the characteristic impedance of the
high-frequency signal passed by the first lead wire 31 can be
controlled to the standard level of 50 Ohm. This embodiment of the
transmission lines 34 reduces the diameter of the bi-wire
structure, thereby reducing the installation density of the jumped
transmission line.
[0032] As shown in FIG. 7, the transmission line 36 comprises the
lead wires 31 and 32, the insulating covering 311 surrounding the
first lead wire 31, the insulating covering 321 surrounding the
second lead wire 32 and an adhesion 37 bounding the coverings 311
and 321 and holding the first lead wire 31 and the second lead wire
32 firmly in parallel. This alternate form achieves the same effect
as the aforesaid first and second embodiments of the present
invention.
[0033] As shown in FIG. 8, the transmission line 38 comprises the
lead wires 31 and 32, the insulating covering 311 surrounding the
first lead wire 31 and the insulating covering 321 surrounding the
second lead wire 32. The covering 311 surrounding the first lead
wire 31 is twisted with the covering 321 surrounding the second
lead wire 32, forming a twisted bi-wire structure. Therefore, the
pitch between the first lead wire 31 and the second lead wire 32 is
equal to the combined wall thickness of the coverings 311 and 321.
Comparing to the aforesaid first, second and third embodiments of
the present invention, the transmission line 38 of this fourth
embodiment requires less installation space.
[0034] Further, the probe holder 20 is adapted to hold the probes
40 and 50 in place and to provide the high-frequency probe card 1 a
common ground potential by means of the grounding plane 21.
Therefore, the grounding plane 21 can be made in any of a variety
of alternate forms. FIG. 9 shows a high-frequency probe card 2
according to a fifth embodiment of the present invention. According
to this fifth embodiment, a probe holder 23 has a locating ring 230
and a grounding plane 231. The locating ring 230 is directly
affixed to the bottom surface 102 of the circuit board 10, having
the same functional structure as the locating ring 22 of the probe
holder 20 in either of the aforesaid first to fourth embodiments of
the present invention. The grounding plane 231 is provided at the
outer peripheral surface of the locating ring 230 for the
connection of the grounding wires 42 and the grounding probes 50,
providing a common ground potential. Because the locating ring 230
is directly affixed to the bottom surface 102 of the circuit board
10, this arrangement eliminates the problem of displacement of the
locating ring 230 relative to the circuit board 10 resulted from
the thermal expansion or contraction of a metal material placed
between the locating ring 230 and the circuit board 10. Therefore,
the locating ring 230 does not displace subject to severe change of
the ambient temperature, and the probes 40 and 50 are constantly
held in position for accurate probing.
[0035] FIG. 10 shows a vertical probe card 3 according to a sixth
embodiment of the present invention. According to this embodiment,
the vertical probe card 3 comprises a circuit board 60, a probe
holder 70, a probe set 80, and transmission lines 30.
[0036] The circuit board 60 having a ring shape defines an annular
outer test zone 601, an annular inner jumping zone 602
concentrically surrounded by the test zone 601, and a center hole
defining a probe zone 603 centered on the circuit board 60 and
surrounded by the jumping zone 602 for accommodating the probe
holder 70. Same as the aforesaid various embodiments of the present
invention, the test zone 601 of the circuit board 60 has signal
circuits 11 and grounding circuits 12 respectively electrically
connected to the first and second lead wires 31 and 32 of the
transmission lines 30. The circuit board 60 further has a plurality
of grounding wires 13 respectively electrically connected to the
grounding circuits 12. The transmission lines 30 and the grounding
wires 13 extend from the test zone 601 to the jumping zone 602 then
to the probe holder 70.
[0037] The probe holder 70 is mounted in the probe zone 603, having
an annular upright sidewall 71 abutted against the periphery wall
of the center hole of the circuit board 60, a bottom wall 72 within
the sidewall 71, a top open chamber 701 defined above the bottom
wall 72 and surrounded by the sidewall 71 for receiving the
transmission lines 30 and the grounding wires 13, a bottom surface
702 defined beneath the bottom wall 72, an insulating layer 73
covered on the top surface of the bottom wall 72, and a grounding
plane 74 covered on the top surface of the insulating layer 73. The
sidewall 71 and the grounding plane 74 are made of metal materials.
The bottom wall 72 and the insulating layer 73 are made of
insulating materials. The bottom wall 72 has a plurality of through
holes 720 each of which has a diameter corresponding to the
diameter of the covering 311 of the first lead wire 31. The first
lead wires 31 with the respective coverings 311 are inserted
through the grounding plane 74 into the inside of the insulating
layer 73 and ended in the respectively through holes 720 of the
bottom wall 72, and then suspending in the bottom surface 702. The
second lead wires 32 are electrically connected to the grounding
plane 74. The grounding wires 13 are electrically connected to the
ground plane 74 and inserted through the insulating layer 73 into
the respectively through holes 720 of the bottom wall 72.
Therefore, the first lead wires 31 and the grounding wires 13 are
respectively exposed on the bottom surface 702.
[0038] The probe set 80 is installed on the bottom surface 702 of
the probe holder 70, including a plurality of signal probes 81 and
a plurality of grounding probes 82. The signal probes 81 and the
grounding probes 82 are respectively made of metal material having
a predetermined hardness. The signal probes 81 and the grounding
probes 82 are perpendicularly fastened to two insulating locating
plates 83. A rear end 810 of each signal probe 81 is connected to
the first lead wire 31 in the respective through hole 720. A rear
end 820 of each grounding probe 82 is connected to the grounding
wire 13 in the respective through hole 720. Further, a plurality of
tips 811 and 821 of the respective probes 81 and 82 are suspending
beneath the lower locating plate 83 for touching test samples.
[0039] Thus, the probe card 3 uses the transmission lines 30 to
directly pass test signals to the signal probes 81 and then the
test samples. This embodiment eliminates the aforesaid solder pads
105 and 106 at the jumping zone 104 of the circuit board 10 to have
the test signal transmitted through the circuit board 10 to the
high-frequency probes 40, thereby preventing dielectric loss
induced by the dielectric material of the circuit board 10 or
return loss resulted from the characteristic impedance mismatching
during signal transmission through different media. Therefore, the
probe card 3 not only allows installation of the transmission lines
30 in a high count manner, but also provides a better reliability
test in the high-frequency signals transmission for maintaining the
characteristic impedance.
[0040] The common ground potential provided by the probe holder 70
is not limited to the arrangement of the grounding plane 74. FIG.
11 shows a probe card 4 according to a seventh embodiment of the
present invention. This embodiment eliminates the grounding plane
74 from the probe holder 70, and directly uses the sidewall 71 to
provide the desired common ground potential, i.e., the second lead
wires 32 and the grounding wires 13 are electrically connected to
the sidewall 71, and the sidewall 71 is electrically connected to
the grounding probes 82. This embodiment achieves the same effects
as the aforesaid sixth embodiment of the present invention.
[0041] Although particular embodiments of the invention have been
described in detail for purposes of illustration, various
modifications and enhancements may be made without departing from
the spirit and scope of the invention. Accordingly, the invention
is not to be limited except as by the appended claims.
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